Data supplied to a central processing unit of data processing system by elements external to the central processing unit, e.g., terminals, are derived in an external data coding format but are processed by the central processing unit in an internal data coding format. Generally, a programmer who inserts data into a data processing system, handles these data in a so-called "external" data coding format which assists the programming work of the programmer. For every data processing system of which I am aware, the external data coding format differs from the internal or machine data coding format. Thus, in most data processing systems a change from an external data coding format to an internal data coding format requires a special sub-routine which is generated by a "compiler". The sub-routine enables a source program written in an evolved language to be translated into an object program written in a machine language of the central processing unit which implements the source program. The compiler generates a sub-routine for translating the data coding format which is phrased in source language by the programmer or included in input-output procedures of the data processing system. The generation of the sub-routine by the compiler lengthens the time required to insert data into the data processing system in a troublesome manner. In the same manner, signals processed by the central processing unit and available to be coupled to an output of the central processing unit, for example on a data bus, are expressed in the internal data coding format. In most cases, the data derived by the central processing unit are utilized by and supplied to an external apparatus, such as a terminal. To enable the external apparatus to use the data derived by the central processing unit, the data signals derived by the central processing unit must be translated from the internal data coding format or machine data coding format into data signals expressed in an external data coding format that corresponds with the format employed by the external apparatus. Consequently, it is necessary for a double translation to be performed at the input as well as the output of the central processing unit to enable the central processing unit to process the data signals supplied to it and to change the data signals it derives into signals which can be utilized by external apparatus. This double translation is protracted and costly.
An object of the present invention is to provide a new and improved apparatus for translating signals between a central processing unit and devices external to the central processing unit.
Another object of the invention is to provide an apparatus for translating data between a central processing unit and apparatus external to the central processing unit without employing a compiler.
A more particular object of the invention is to provide a new and improved apparatus for translating numeral representing signals between a central processing unit and apparatus external to the central processing unit wherein the central processing unit has an internal code with a signless condensed format.
Still another object of the invention is to provide an apparatus for converting numeral representing signals exchanged between a central processing unit and apparatus external to the central processing unit by treating the signals internally of the central processing unit.
Still a further object of the invention is to provide an apparatus for converting signals in an external data coding format supplied to a central processing unit by a device external to the central processing unit into signals having an internal data coding format by treating the signals internally of the central processing unit.
Still a further object of the invention is to provide an apparatus for converting signals derived by a central processing unit in an internal data coding format into signals that are supplied to a device external to the central processing unit in an external data coding format by a treatment internal to the central processing unit.